| NRA | nitrate reductase; nucleus retroambigualis |
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| NRGC | nucleus reticularis gigantocellularis |
| NRL | nucleus reticularis lateralis |
| NRM | National Registry of Microbiologists; normal range of motion; nucleus reticularis magnocellularis |
| NRP | nucleus reticularis parvocellularis |
| nucleus motorius nervi trigemini | <anatomy, nerve> A group of motor neurons innervating the muscles of mastication (masseter, temporalis, internal and external pterygoid muscles) and the musculi tensor tympani and tensor veli palatini. The nucleus lies in the upper pontine tegmentum medial to the main sensory nucleus of the trigeminus. Synonym: nucleus motorius nervi trigemini, masticatory nucleus, motor nucleus of trigeminus, nucleus masticatorius. (05 Mar 2000) |
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| nucleus nervi abducentis | Nucleus of abducent nervenucleus abducentis, a group of motor neurons in the lower part of the pons, innervating the lateral rectus muscle of the eye; unique among motor cranial nerve nuclei in that it consists of two distinct populations of neurons: neurons that give rise to fibres forming the abducens nerve root and those internuclear neurons whose processes cross the midline, ascend in the opposite medial longitudinal fasciculus, and terminate upon specific oculomotor neurons; considered a primary centre for mechanisms controlling conjugate horizontal gaze. Synonym: nucleus nervi abducentis. (05 Mar 2000) |
| nucleus nervi facialis | A group of motor neurons located in the ventrolateral region of the lower pontine tegmentum and innervating the facial muscles, the stapedius muscle in the middle ear, the posterior limb of the musculus digastricus, and the stylohyoid muscle. Synonym: nucleus nervi facialis, facial motor nucleus, motor nucleus of facial nerve, nucleus facialis. (05 Mar 2000) |
| nucleus nervi hypoglossi | The motor nucleus innervating the intrinsic and four of the five extrinsic muscles of the tongue; it is located in the medulla oblongata near the midline, immediately beneath the floor of the inferior recess of the rhomboid fossa. Synonym: nucleus nervi hypoglossi, nucleus of hypoglossal nerve. (05 Mar 2000) |
| nucleus nervi oculomotorii | The composite group of motor neurons innervating all of the external eye muscles except the musculus rectus lateralis and musculus obliquus superior, and including the musculus levator palpebrae superioris; the most rostral component of the nucleus is the Edinger-Westphal nucleus which innervates the musculi sphincter pupillae and ciliaris via the ciliary ganglion. The oculomotor nucleus lies in the rostral half of the midbrain, near the midline in the most ventral part of the central gray substance; fibres of the medial longitudinal fasciculus form its lateral borders. Synonym: nucleus nervi oculomotorii, nucleus of oculomotor nerve. (05 Mar 2000) |
| nucleus nervi trochlearis | A group of motor neurons innervating the superior oblique muscle of the contralateral eye. The nucleus lies in the caudal half of the midbrain, behind the oculomotor nucleus, in the most ventral part of the central gray substance, near the midline. Synonym: nucleus nervi trochlearis, nucleus of trochlear nerve. (05 Mar 2000) |
| nucleus niger | A large cell mass, crescentic on transverse section, extending forward over the dorsal surface of the crus cerebri from the rostral border of the pons into the subthalamic region; it is composed of a dorsal stratum of closely spaced pigmented (i.e., melanin-containing) cells, the pars compacta, and a larger ventral region of widely scattered cells, the pars reticulata; the pars compacta in particular includes numerous cells that project forward to the striatum (caudate nucleus and putamen) and contain dopamine, which acts as the transmitter substance at their synaptic endings; other, apparently non-dopaminergic cells of the substantia nigra project to a rostral part of the ventral nucleus of thalmus, the middle layers of the superior colliculus and to restricted parts of the reticular formation of the midbrain; the nigrostriatal projection is reciprocated by a massive striatonigral fibre system with multiple neurotransmitters, chief among which is gamma-aminobutyric acid (GABA); substantia n. Receives smaller afferent projections from the subthalamic nucleus, the lateral segment of the globus pallidus, the dorsal nucleus of the raphe and the pedunculopontine nucleus of the midbrain. The pars reticulata forms part of the output system for the striate body. The substantia n. Is involved in the metabolic disturbances associated with Parkinson's disease and Huntington's disease. Synonym: locus niger, nucleus niger, Soemmerring's ganglion. (05 Mar 2000) |
| nucleus of cuneate fasciculus | The larger Burdach's nucleus; one of the three nuclei of the posterior column of the spinal cord; located near the dorsal surface of the medulla oblongata at and below the level of the obex, the nucleus receives posterior root fibres corresponding to the sensory innervation of the arm and hand of the same side; together with its medial companion, the gracile nucleus, it is the major source of origin of the medial lemniscus. Synonym: nucleus cuneatus, Burdach's nucleus, nucleus funiculi cuneati, nucleus of cuneate fasciculus. (05 Mar 2000) |
| nucleus of Darkschewitsch | An ovoid cell group in the ventral central gray substance rostral to the oculomotor nucleus, receiving fibres from the vestibular nuclei by way of the medial longitudinal fasciculus; projections are not known, although some cross in the posterior commissure. (05 Mar 2000) |
| nucleus of Goll | The medial one of the three nuclei of the dorsal column, the remaining two being the cuneate nucleus and the accessory cuneate nucleus, which corresponds to the clava; it receives dorsal-root fibres conveying sensory innervation of the leg, and lower trunk, and projects, by way of the medial lemniscus, to the ventral nucleus posterior nucleus of the thalamus. Synonym: nucleus gracilis, nucleus fasciculi gracilis, nucleus funiculi gracilis, nucleus of Goll. (05 Mar 2000) |
| nucleus of hypoglossal nerve | The motor nucleus innervating the intrinsic and four of the five extrinsic muscles of the tongue; it is located in the medulla oblongata near the midline, immediately beneath the floor of the inferior recess of the rhomboid fossa. Synonym: nucleus nervi hypoglossi, nucleus of hypoglossal nerve. (05 Mar 2000) |
| nucleus of inferior colliculus | The nerve cell groups composing the colliculus inferior. Synonym: nucleus colliculi inferioris. (05 Mar 2000) |
| nucleus of lateral geniculate body | Nucleus of the thalamus characterised by six layers of cells, two parvicellular, four magnocellular, alternating with thin layers of fibres; receives bilateral visual input, projects to calcarine cortex. (05 Mar 2000) |
| nucleus of lateral lemniscus | A substantial cell mass embedded in the lateral lemniscus, immediately below the latter's entry into the inferior colliculus; the nucleus represents a synaptic way-station for part of the fibres of the lateral lemniscus. Synonym: nucleus lemnisci lateralis. (05 Mar 2000) |
| nucleus of lens | The core or inner dense portion of the lens of the eye. Synonym: nucleus of lens. (05 Mar 2000) |